1. Field of the Invention
The present invention relates to an apparatus for use in replacing a ring gasket carried by a subsea wellhead connector near the ocean floor.
2. Description of the Prior Art
In the drilling of oil and gas wells at an underwater site, a coupling is used for connecting subsea wellhead components to one another in sealed or pressure tight relation. It is usual for the upper portion of the coupling to contain a seal or ring gasket retained in place by a suitable device, this ring gasket being brought into sealing relation with a lower device previously installed at the underwater location. The ring gasket used in the coupling may commonly be designated as a "RX", "CX", "AX" or "VX" ring gasket depending upon the manufacturer of the gasket.
When the underwater coupling is disconnected, it is desirable to replace the previously installed ring gasket with a new one to insure a pressure tight fit upon re-engagement of the coupling assembly. It is also desirable to inspect the surface of the old gasket for unusual deformations that would indicate damage to the sealing shoulders which mate with the gasket. After the underwater coupling is disconnected, the entire upper portion of the wellhead connector coupling with its attached ring gasket may be retrieved to the deck of a surface vessel conducting the well operations.
The ring gasket is usually removed from a ring gasket retainer assembly, such as the one disclosed in U.S. Pat. No. 3,350,103, entitled "Seal Ring Holding Device", issued Oct. 31, 1967 to A. G. Ahlstone. The ring gasket is removed by disengaging a split ring from a circumferential groove formed in the outer surface of the ring gasket.
In shallow water depths, the retrieval operation does not cause an unnecessary amount of downtime. However, in deeper waters, to retrieve the ring gasket retainer assembly all the way to the surface in order to remove the old ring gasket would require considerable time and entail great expense because of the large cost of offshore operations. Even in shallow waters removal by divers is impractical due to the weight (50-80 lbs). of the ring gaskets normally used for subsea connections.
Accordingly, it is desirable to present a method and apparatus for installing a new ring gasket into a subsea coupling, without having to retrieve the coupling to the surface along with the thousands of feet of pipe to which it is connected at a cost of up to a million dollars. It is also desirable to retrieve the previously installed ring gasket for inspection and from a depth generally below that at which a diver can operate, say, 5,000 feet or more.